The purpose of this research is to conduct biochemical investigations of the transformation-specific alterations in the surface constituents of animal cells and to determine how these changes relate to the altered growth properties and tumorigenicity of transformed cells. In this context we are now investigating the changes in the membrane glycoproteins of BHK cells grown under various conditions by analyzing labeled glycopeptides by two-dimensional gel electrophoresis, and studying the kinetics of synthesis and turnover of cell surface constituents. A separate aspect of our study involves the characterization of cell-surface glyco -syltransferases which might play a role in density-dependent regulation of growth control. BIBLIOGRAPHIC REFERENCES: Datta, P. (1974) Labeling of External Surface of Mouse and Hamster Fibroblasts with C14-Sialic Acid, Biochemistry 13, 3987.